摘要：Oil sand extraction in Alberta, Canada is a multibillion dollar industry operating over 143 km2 of open pit miningand 4600 km2 of other bitumen strata in northern boreal forests. Oil production contributes to Canada-wide GDP, creates socio-cultural problems, provides energy exports and employment, and carries environmental risks regarding long-term reclamationuncertainties. Of particular concern are the implications for wetlands and water supply management. Mining of oil sands is veryattractive because proven reserves of known quality occur in an accessible, politically stable environment with existinginfrastructure and an estimated 5.5 billion extractable barrels to be mined over the next five decades. Extraction occurs under aset of limiting factors or thresholds including: limited social tolerance at local to international levels for externalities of oil sandproduction; water demands > availability; limited natural gas supplies for oil processing leading to proposals for hydroelectricdams and nuclear reactors to be constructed; difficulties in reclaiming sufficient habitat area to replace those lost. Replacementof the 85 km2 of peat-forming wetlands forecast to be destroyed appears unlikely. Over 840 billion liters of toxic fluid byproductsare currently held in 170 km2 of open reservoirs without any known process to purify this water in meaningful time frames evenas some of it leaches into adjacent lands and rivers. Costs for wetland reclamation are high with estimates of $4 to $13 billion,or about 6% of the net profits generated from mining those sites. This raises a social equity question of how much reclamationis appropriate. Time frames for economic, political, and ecological actions are not well aligned. Local people on or near minesites have had to change their area use for decades and have been affected by industrial development. Examining mining effectsto estimate thresholds of biophysical realities, time scales, economic allocations, and social tolerance helps to contextualize theneeds for decision making and relevant policy formation as a way of constructively reconciling production with governingsafeguards to the environment and citizens
关键词：environmental constraints; limits; oil sands; reclamation; thresholds; time frames
